The recessed incandescent lighting fixture has achieved a high degree of acceptance for use in commercial installations, offices and homes where effective lighting is required without visibly intruding into the room. These fixtures are concealed within the ceiling and present only an attractive trim surface to the room below along with a light pattern depending upon the requirements of the user. Suitable lens and louvres often conceal the lamp from view.
Mechanical installation of the recessed lighting unit is usually accomplished by means of some support bridging between a pair of adjacent ceiling joists. In the past, two general types of hangers have been used. Classically, a U-shaped bar approximately 3/8 of an inch by 1/8 with end feet have been used to support various types of lighting fixtures. The end feet rest in notches on the top of joists and the fixture is secured to the bottom of the U at various screw holes. This type of recessed fixture support had several disadvantages, one being that the installation time was unnecessarily long since the installer had to chisel 4 notches in the four joists. Also, the installer had to have access to the top of the ceiling joists.
More recently hanger bars have been built as part of the fixture. Typically these hanger bars include a pair of bars members, each with an end foot bent horizontally to engage the inner faces of ceiling joists. Typically the two hanger bars overlap and include saw tooth notches in the top edge. The installer extends the two hanger bar members into engagement with the joists, nails them to the joists and then crimps fingers built into the fixture frame into the saw tooth edges to hold the fixture in place. Typically such hangers did not provide adequate support in the vertical direction causing fixtures to sag, and did not allow full freedom of the adjustment of the fixture from one edge of the inter-joist space to the other. Typically these hangers were located at varying distances above the plane of the lower edge of the joists so they could not be used as a guide to the vertical location of the fixture. Installation of recessed fixture, if not at the appropriate position vertically and in the plane of the ceiling, provided an unattractive installation.